A conventional micro-fluid ejection device such as an ink jet printhead generally has flow features either formed in a thick film layer deposited on a semiconductor substrate containing ink ejection devices or flow features ablated along with nozzles holes in a polymeric nozzle plate material. The term “flow features” is used to refer to ink chambers and ink supply channels that provide a fluid such as ink to ejection devices on the semiconductor substrate for ejection through nozzle holes. When both the nozzle holes and flow features are ablated in the nozzle plate material, a thick film material is not present. A disadvantage of forming the flow features and nozzle holes in the nozzle plate material is that the flow feature height and nozzle bore length are constrained by the nozzle plate material thickness. For printheads having a separate thick film layer and nozzle plate with the flow features formed in a thick film layer, the nozzle bore length is equal to the nozzle plate material thickness and the flow feature dimensions are constrained by the thickness of the thick film layer.
Another conventional printhead includes a planarization layer in addition to the nozzle plate material. The planarization layer was typically no more than about 2.5 microns thick. Accordingly, a small percentage of the total flow feature height dimension was formed in the planarization layer. However, the maximum percentage of the flow feature height dimension formed in the planarization layer was less than about 12 percent. Accordingly, the flow feature characteristics were effectively controlled by the thickness of the nozzle plate material and the dimensions of the flow features in the nozzle plate material.
Unfortunately, there are limited choices available for the nozzle plate material thickness. Chemical inertness to ink, adhesive ability, vendor availability, part durability, cost, and many other factors play a part in determining a suitable nozzle plate material and its thickness. Accordingly, there is often only one preferred material and only a select few nozzle plate material thicknesses available. The restriction on nozzle plate material thickness often leads to compromises in flow feature design and/or nozzle dimensions which may lead to reduced printhead performance and suboptimal performance.
As the speed of micro-fluid ejection devices such as ink jet printers increases, the frequency of ink ejection by individual heating elements also increases requiring more rapid refilling of the ink ejection chambers. Hence, there exists a need for improved micro-fluid ejection devices and methods for making the devices.